This invention relates to protective coatings for objects, and particularly to protective coatings for components in disc drive systems used for the storage and/or retrieval of data, including, for example, read/write heads and storage discs.
Advances in many technologies have created enhanced demands on materials used in the production of a variety of devices. Specifically, miniaturization has decreased tolerance levels while increasing performance requirements. Coating technology has become extremely important since coatings can be used to alter the surface properties of the composite while maintaining desirable properties of the underlying substrate. In particular, thin coatings can serve to protect the underlying substrate from a variety of assaults.
Rotating magnetic, optical and optical-magnetic data storage devices use data storage discs with heads mounted to aerodynamic sliders to read data to and/or write data from the disc. The slider includes an air bearing surface that confronts the disc surface. In use, the slider xe2x80x9cfliesxe2x80x9d a predetermined distance above the disc while the disc is spinning at a rapid rate.
Disc drives for data storage can use one or more discs with a medium for the storage of information. In the case of a magnetic or magneto-optical disc drive, the medium includes a relatively thin magnetic layer on a non-magnetic substrate. The data are stored at specific locations along concentric data tracks, usually within data storage zones.
Intermittent contact between the slider and the disc surface causes wear of the disc surface and of the slider. To protect the disc surface and/or the slider from wear and corrosion, overcoats are placed over the magnetic medium on the disc surface and/or the slider surface, including the head. Preferred overcoats reduce wear, friction and oxidation of the slider and disc while maintaining proper aerodynamic interaction between the slider and the disc surface during rotation and during take-off and landing. Protective overcoats are also applied to heads and sliders to protect the head during processing and fabrication.
To obtain higher storage densities on the disc surface, fly heights between the read/write head and the disc surface are being reduced. For example, it is not unusual to require fly heights as small as 10 nanometers (nm) for high density disc drives. Reducing the fly height improves the magnetic interaction between the head and the disc surface to allow correspondingly higher data storage densities. Thus, it is important that protective coatings are thin enough not to excessively increase the effective distance between the magnetic transducers of the head and the magnetic materials near the disc surface. Consequently, where fly heights of 10 nm are required, the protective coating should be thin, preferably not greater than 1 nm.
Carbon coatings have been used to form protective layers on substrates. The coating, however, increases the spacing between the surface and the underlying substrate. Thus, for example in the production of magnetic discs, any performance improvement resulting from a reduction in fly height can be countered by the presence of protective coatings and the like that result in an increased distance between the head and the magnetic medium.
More recently, fullerene has been explored as a potential coating material for magnetic devices such as magnetic discs in a disc drive. U.S. Pat. No. 5,374,463, for example, describes magnetic discs with film coatings formed of multilayer fullerene having a thickness between about 30 and 150 Angstroms (3 to 15 nanometers). However, the multilayer fullerene coatings described therein are simply too thick for present disc drive fly height requirements. The present invention provides a solution to this and other problems, and offers other advantages over the prior art.
The present invention is directed to a process of forming a coating on a substrate. A multilayer coating of fullerene molecules is deposited on the substrate, and layers of the multilayer coating are removed leaving an approximate monolayer coating of fullerene molecules on the substrate. Preferably, the fullerene is removed while the temperature of the substrate remains below at least about 200xc2x0 C.
In some embodiments, a beam generator is adjusted to produce a beam arranged to break the fullerene-to-fullerene intermolecular bond of the multilayer coating and inadequate to break the fullerene-to-substrate association/bond of the coating. The beam is directed at the multilayer coating to break the fullerene-to-fullerene intermolecular bond.
In one embodiment, the beam generator is an ion beam generator/ion source that is adjusted to produce a beam having a current density between about 0.05 and 5.0 mA. In other embodiments, the beam generator is a laser beam generator or a gas ion cluster beam generator.
In another embodiment, the monolayer of fullerene molecules is formed by applying a solvent to the multilayer coating. The solvent has a strength adequate to break the fullerene-to-fullerene intermolecular bond of the multilayer coating and inadequate to break the fullerene-to-substrate association/bond of the coating to thereby dissolve the fullerene in the coating that is not bonded to the substrate.